On Mon, Aug 30, 2021 at 3:38 PM Jonas Dreßler <verdre@xxxxxxx> wrote: > > On the 88W8897 card it's very important the TX ring write pointer is > updated correctly to its new value before setting the TX ready > interrupt, otherwise the firmware appears to crash (probably because > it's trying to DMA-read from the wrong place). > > Since PCI uses "posted writes" when writing to a register, it's not > guaranteed that a write will happen immediately. That means the pointer > might be outdated when setting the TX ready interrupt, leading to > firmware crashes especially when ASPM L1 and L1 substates are enabled > (because of the higher link latency, the write will probably take > longer). > > So fix those firmware crashes by always forcing non-posted writes. We do > that by simply reading back the register after writing it, just as a lot > of other drivers do. > > There are two reproducers that are fixed with this patch: > > 1) During rx/tx traffic and with ASPM L1 substates enabled (the enabled > substates are platform dependent), the firmware crashes and eventually a > command timeout appears in the logs. That crash is fixed by using a > non-posted write in mwifiex_pcie_send_data(). > > 2) When sending lots of commands to the card, waking it up from sleep in > very quick intervals, the firmware eventually crashes. That crash > appears to be fixed by some other non-posted write included here. Thanks for all this work! Nevertheless, do we have any commits that may be a good candidate to be in the Fixes tag here? > Signed-off-by: Jonas Dreßler <verdre@xxxxxxx> > --- > drivers/net/wireless/marvell/mwifiex/pcie.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.c b/drivers/net/wireless/marvell/mwifiex/pcie.c > index c6ccce426b49..bfd6e135ed99 100644 > --- a/drivers/net/wireless/marvell/mwifiex/pcie.c > +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c > @@ -237,6 +237,12 @@ static int mwifiex_write_reg(struct mwifiex_adapter *adapter, int reg, u32 data) > > iowrite32(data, card->pci_mmap1 + reg); > > + /* Do a read-back, which makes the write non-posted, ensuring the > + * completion before returning. > + * The firmware of the 88W8897 card is buggy and this avoids crashes. Any firmware version reference? Would be nice to have just for the sake of record. > + */ > + ioread32(card->pci_mmap1 + reg); > + > return 0; > } -- With Best Regards, Andy Shevchenko
